36.4.5 Daisy-Chain Configuration

The SPI bus can be connected in a daisy-chain configuration, where the first client output is connected to the second client input, the second client output is connected to the third client input, and so on. The final client output is connected to the host input. Each client sends out, during a second group of clock pulses, an exact copy of what was received during the first group of clock pulses. The whole chain acts as one large communication shift register. The daisy-chain feature only requires a single Client Select line from the host device connected to all client devices (alternately, the client devices can be configured to ignore the Client Select line by setting the SSET bit).

In a typical daisy-chain configuration, the SCK signal from the host is connected to each of the client device SCK inputs. However, the SCK input and output are separate signals selected by the PPS control. When the PPS selection is made to configure the SCK input and SCK output on separate pins, the SCK output will follow the SCK input, allowing for SCK signals to be daisy-chained like the SDO/SDI signals.

The following two figures show block diagrams of a typical daisy-chain connection and a daisy-chain connection with daisy-chained SPI clocks, respectively.